64,192 research outputs found
Determination of total and polycyclic aromatic hydrocarbons in aviation jet fuel
No full textThe aviation jet fuel widely used in turbine engine aircraft is manufactured from straight-run kerosene. The combustion quality of jet fuel is largely related to the hydrocarbon composition of the fuel itself; paraffins have better burning properties than aromatic compounds, especially naphthalenes and light polycyclic aromatic hydrocarbons (PAHs), which are characterised as soot and smoke producers. For this reason the burning quality of fuel is generally measured as smoke formation. This evaluation is carried out with UV spectrophotometric determination of total naphthalene hydrocarbons and a chromatographic analysis to determine the total aromatic compounds. These methods can be considered insufficient to evaluate the human health impact of these compounds due to their inability to measure trace (ppm) amounts of each aromatic hydrocarbon and each PAH in accordance with limitations imposed because of their toxicological properties. In this paper two analytical methods are presented. Both are based on a gas chromatographic technique with a mass detector operating in the selected ion monitoring mode. The first method was able to determine more than 60 aromatic hydrocarbons in a fuel sample in a 35-min chromatographic run, while the second was able to carry out the analysis of more than 30 PAHs in a 40-min chromatographic run. The linearity and sensitivity of the methods in measuring these analytes at trace levels are described. (C) 2002 Elsevier Science B.V. All rights reserved
Bone Marrow Fibrosis and Early Hematological Response as Predictors of Poor Outcome in Azacitidine Treated High Risk-Patients With Myelodysplastic Syndromes or Acute Myeloid Leukemia
No full textAzacitidine (AZA) treatment is effective treatment for patients with myeloid disorders, and factors predictive of treatment outcome are under investigation. Little is known about the effect of bone marrow fibrosis on response to AZA therapy. We, retrospectively, evaluated clinical predictors of overall survival (OS) and overall response rate (ORR) for patients treated with AZA in a real-life cohort. We evaluated 94 consecutive patients treated with AZA outside of clinical trials (75 mg/m 2 /day for 7 days every 28 days; 5 + 2 + 2 schedule), from June 2009 to February 2016. Ninety-three patients were evaluated for response. After a median of 6 cycles, ORR—complete response (CR; including marrow CR) + partial response (PR) + hematological improvement (HI)—was 41.9% (CR = 18.3%; PR = 11.8%; HI = 11.8%). Stable disease was observed in 21.5%, and failure in 36.5%. Pre-AZA bone marrow blast percentage, International Prognostic Scoring System (IPSS) or IPSS-R category, and time from diagnosis to AZA had no effect on response. Median OS from start of therapy was 18.5 months, and was significantly related to higher IPSS category (P =.01), poor cytogenetics according to the IPSS (P =.01), poor and very poor cytogenetics according to the IPSS-R (P =.02), and lower ORR (P =.006). Patients with MF-0 pre-AZA demonstrated significantly higher ORR, (CR + PR + HI) and stable disease, and lower failure rates than those with any grade of fibrosis. Indeed, cases with pre-AZA fibrosis > MF-1 had shorter OS (P =.005). Achievement of HI before 4 cycles of treatment negatively impacted OS (P =.009)
Blended learning with MOOCs: From investment effort to success: a systematic literature review on empirical evidence
No full textThis paper reports on a systematic literature review by analysing 48 empirical studies on the use of Blended Learning with MOOCs. The results report on the pedagogically motivated, infrastructural and design-intensive efforts of the institutions. Moreover, they empirically confirm previously made claims that within hybrid initiatives, Flipped Classroom model is the most used one. They also indicate that blended learning in the context of MOOCs yields positive results. At the same time, most of the reviewed empirical research uses so called “MOOCs as Driver” model, where a traditional course in the curriculum is organized around a MOOC.</p
Disentangling the solar activity-solar wind predictive causality at Space Climate scales
No full textThe variability in the magnetic activity of the Sun is the main source of the
observed changes in the plasma and electromagnetic environments within the
heliosphere. The primary way in which solar activity affects the Earth's
environment is via the solar wind and its transients. However, the relationship
between solar activity and solar wind is not the same at the Space Weather and
Space Climate time scales. In this work, we investigate this relationship
exploiting five solar cycles data of Ca II K index and solar wind parameters,
by taking advantage of the Hilbert-Huang Transform, which allows to separate
the contribution at the different time scales. By filtering out the high
frequency components and looking at decennial time scales, we confirm the
presence of a delayed response of solar wind to Ca II K index variations, with
a time lag of ~ 3.1-year for the speed and ~ 3.4-year for the dynamic pressure.
To assess the results in a stronger framework, we make use of a Transfer
Entropy approach to investigate the information flow between the quantities and
to test the causality of the relation. The time lag results from the latter are
consistent with the cross-correlation ones, pointing out the presence of a
statistical significant information flow from Ca II K index to solar wind
dynamic pressure that peaks at time lag of 3.6-year. Such a result could be of
relevance to build up a predictive model in a Space Climate context
Effect of premolar extraction and anchorage type for orthodontic space closure on upper airway dimensions and position of hyoid bone in adults: a retrospective cephalometric assessment
No full textBackground. This study aimed to assess the effect of premolar extraction and anchorage type for orthodontic space closure on upper airway dimensions and position of hyoid bone in adults by cephalometric assessment. Methods. This retrospective study was conducted on 142 cephalograms of patients who underwent orthodontic treatment with premolar extraction in four groups of (I) 40 class I patients with bimaxillary protrusion and maximum anchorage, (II) 40 class I patients with moderate crowding and anchorage, (III) 40 class II patients with maximum anchorage, and (IV) 22 skeletal class III patients with maximum anchorage. The dimensions of the nasopharynx, velopharynx, oropharynx, and hypopharynx, and hyoid bone position were assessed on pre- and postoperative lateral cephalograms using AudaxCeph v6.1.4.3951 software. Data were analyzed by the Chi-square test, paired t-test, and Pearson's correlation test (alpha D 0.05). Results. A significant reduction in oropharyngeal, velopharyngeal, and hypopharyngeal airway dimensions was noted in groups I, III, and IV (P <0:001), which was correlated with the magnitude of retraction of upper and lower incisors (r =0:6-0:8). In group II, a significant increase was observed in oropharyngeal and velopharyngeal dimensions (P < 0:001). A significant increase in nasopharyngeal dimensions occurred in all groups (P < 0:001). Also, in groups I and III, the position of hyoid bone changed downwards and backwards, which was correlated with reduction in airway dimensions (r =0:4-0:6). Conclusion. According to the present results, extraction orthodontic treatment affects upper airway dimensions and hyoid bone position. Maximum anchorage decreases airway dimensions while moderate anchorage increases airway dimensions
Thermal expansion anomalies of R(Fe, M)(12) (R=Y, Nd; M=Mo and Si)
No full textStructural and thermal-expansion anomaly studies on R(Fe,M)(12) (R=Nd and and Y, M=Mo and Si) compounds were performed by x-ray diffraction. Mo atoms occupy the 8i site. While Si atoms occupy the 8f and 8j sites but not the 8i site. Thermal-expansion anomaly shows only in ab plane in the Mo compounds, while becomes very weak and along with only the c axis in the Si compounds. The anomaly was attributed to the contribution of the interactions of short Fe-Fe distances similar to the previous explanation on other R-Fe intermetallics and that of other strongly positive interactions such as 8j-8j. (c) 2005 American Institute of Physics.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000230168300025&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, AppliedSCI(E)EICPCI-S(ISTP)
Dentin thickness of the danger zone in the mesial roots of the mandibular molars: a cone beam computed tomography analysis
No full textBACKGROUND: Mandibular first molars appear to be the most commonly tooth subjected to a root canal treatment, therefore a better understanding of the anatomy critical zones for resistance of this teeth may decrease the treatment's failure rate. So, this study was conducted to evaluate the dentin thickness of the danger zone in mesial roots of mandibular first molars using cone beam computed tomography in an Iranian population. METHODS: In this cross-sectional study, 210 Cone Beam Computed Tomography acquisition of the mandibular first molars were collected from a radiology center in Qazvin. The dentin thickness of the mesial roots (mesiobuccal and mesiolingual canals) was measured from the furcation to 5 mm below. The relationship between the dentin thickness in the danger zone and parameters, like age, gender, placement side, root length, the curvature of the canal, canal type, presence of middle mesial canal, and distance between the orifices of the mesial canals was investigated. Frequency, mean and standard deviation for variables were calculated, and data analysis was done by SPSS using simple and multiple linear regression and Pearson correlation coefficient. Also, two-sample t-test was used to compare mesiobuccal and mesiolingual on two sides. The significant level was also considered at (p < 0.05). RESULTS: The average minimum thickness of danger zone dentin was found to be 0.885 ± 0.259 mm in the mesiobuccal canal and 0.906 ± 0.206 mm in the mesiolingualcanal. Also, the minimum thickness of dentin in the mesiobuccal and mesiolingual canals in the range of 0 to 1 mm from the furcation was more than in other areas. There was no significant relationship between the minimum dentin thickness of the danger zone with gender, placement side, root length, canal type, and mesial canal entrance distance. But with increasing age, the thickness of dentin in the danger zone in the mesiolingualcanal increased significantly (p = 0.008). It was also observed that with the increase in the curvature of the canal, the thickness of the dentin in the danger zone in the mesiobuccal canal decreased (moderately curved (p = 0.008), severely curved (p = 0.046)). In addition, the thickness of the dentin in the mesiobuccal and mesiolingual canal was less in the samples with the middle mesial canal (p = 0.047, 0.044). CONCLUSIONS: Less dentin thickness in the danger zone in the mesial roots of mesiolingual mandibular first molars was seen in younger patients in mesiolingual canal, with a greater degree of canal curvature in the mesiobuccal canal and teeth with a middle mesial canal. Therefore, it is suggested that large taper instruments should be used with more precision to prevent complications
La lobectomia con la plastica bronchiale e vascolare: analisi retrospettiva di un’esperienza monocentrica
No full textLa lobectomia con la plastica bronchiale e vascolare: analisi retrospettiva di un’esperienza monocentric
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